Apparatus for performing well operations



March 1967 J. B. M ELHENY APPARATUS FOR PERFORMING WELL OPERATIQIIS 2 Sheets-Sheet 1 Filed Aug. 9, 1965 FiGZ.

JOHN B. MC ELHENY INVENTOR. KENDRICK, SCHRAMM $,STOLZY ATTORNEY.

March 28, 1967 j MCELHENY APPARATUS FOR PERFORMING WELL OPERATIONS 2 Sheets-Sheet 2 Filed Aug. 9, 1965 Elll I'll-Il llllllllll ll-I'l JOHN B, MCELHENY INVENTOR. KENDRICK, SCHRAMM @STOLZY ATTORNEY.

United States Patent 3,311,178 APPARATUS FGR PERFGRMING WELL OiERATIONS John B. McElheny, Anaheim, Caiif., assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Filed Aug. 9, 1965, Ser. No. 482,987 4 Claims. (Cl. 1754.54)

This application is a continuation-im art of applicants copending application Ser. No. 132,492, filed Aug. 18, 1961.

This invention relates to the art of performing operations in bore holes, and more particularly to a method of and a device for creating circulation fluid pressures of large fluctuating magnitudes.

Although the tool of the present invention may have a much larger scope of application, it has been found to be unusually useful when employed with gun and shaped charge perforators, especially the former.

In the past, it has been the practice to detonate the explosive charge of a perforator while the body of the tool is suspended at a depth of several thousand feet in a well bore filled with drilling mud. In such a case, perforator penetration is severely limited by the extremely high pressures created around the tool by the relatively large column of drilling mud located above it. t

The device of the present invention overcomes the above-described and other disadvantages of the prior art by reducing drilling mud hydrostatic pressure, e.g. around a perforator. Thus, if the perforator is tired while the drilling mud static pressure is reduced, substantially improved penetration may be achieved.

In addition to improving perforator penetration, it is an advantage of the method of the present invention that formation fluid under formation pressure may flow from a formation when the drilling mud hydrostatic pressure is reduced in the well. The same may produce a cleaning or fracturing eflect for purposes other than perforating as well as for perforating and in combination with other tools.

In accordance with a special feature of the invention, a hollow body is lowered into a well with a perforator and the body opened to permit an inrush of well circulation fluid at the position of the perforator. In this case, not only is the pressure around the perforator momentarily reduced, but after the perforator has been fired and per forations made in the wall of the well bore the dynamic pressure therearound is subsequently increased. Such an increase is beyond the static pressure of the circulation fluid or drilling mud column when motionless, due to the impact of the falling column at the lower limit of its travel in filling the hollow body. Thus, in accordance with an outstanding feature of the present invention, the perforator is fired after the drilling mud pressure is reduced and before it is increased by the impact of the falling rnud column. An advantage of this feature is that the impact has the effect of additionally extending the perforation opening initiated by the perforator.

In accordance with another feature of the invention, detonation of an explosive charge in an electrical device such as a perforator may be performed by means responsive to opening of the hollow body, such a device being responsive to an increase in pressure in the body.

The above-described and other advantages of the present invention will be better understood from the following description when considered in connection with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is an elevational view of a tool made in accordice ance with the invention and with which the method thereof may be carried out;

FIG. 2 is a broken longitudinal sectional view taken on the line 2-2 of the tool shown in FIG. 1;

FIG. 3 is a transverse sectional view taken on the line 33 of the tool shown in FIG. 2, the sectional view of FIG. 2 also being indicated in FIG. 3;

FIG. 4 is a broken longitudinal sectional view of a tool made in accordance with another embodiment of the present invention; and

FIG, 5 is a broken longitudinal sectional view of a tool made in accordance with still another embodiment of the invention.

In FIG. 1, one embodiment of a tool of the invention, is indicated generally at 10. Tool is adapted to be supported in an oil well on a conventional wire line 11. Wire line 11 is fixed to a conventional socket 12, not shown in detail, adapted to engage threads 13 of a circulating head generally indicated at 14 in FIG. 2 to Support head 14 and the other structure of tool 10 therefrom. Circulating head 14 is threaded at 15 into a sleeve 16 into which a connector 17 is threaded at 18, as shown in FIG. '2. A body 19 of a conventional gun perforator is then threaded into the lower end of connector 17 at 20, as shown in FIG. 2.

In FIG. 2, circulating head 14 is shown including, in addition to threads 13, an O-ring 21 located in an external groove 22 in the body of a circulating head 14 to provide a fluid-tight seal with the internal surface of socket 12. When socket 112 is threaded onto the upper end of circulating head 14, the lower end thereof abuts a shoulder 23 on head 14. Circulating head 14 is provided with ports at 24 as shown both in FIGS. 1 and 2 through which drilling mud may flow. As stated previously, the lower end of circulating head 14 is threaded at 15 into sleeve 16, circulating head 14 being provided with a shoulder at 25 to abut the upper end of sleeve 16.

Wire line 11 is the conventional electrical wire line, the same having an insulated conductor at the center and a conductive armor around the conductor to transmit electrical signals to the tool it while mechanically supporting the same in a well. A pair of rod-shaped conductive shafts 26 and 27 are located centrally within the bore 28 of circulating head 14 to transmit electrical signals to an explosive charge 29 located in sleeve 16, as well as for other current carrying purposes, shaft 26 being slidable in an insulating cylinder 30 which abuts a small shoulder 31 within the bore 28 of circulating head 14. Shaft 26 is provided with a flange 32 welded at 33 thereto to prevent shaft 26 from sliding upwardly out of cylinder 30. The lower end of shaft 26 and the upper end of shaft 27 are respectively provided with flanges 34 and 35 welded thereto in the same manner as flange 32 is welded to shaft 26 to retain an open coiled spring 36 therebetween to urge shaft 26 upwardly through cylinder 39 until flange 32 abuts the same. Shaft 26 makes electrical contact with the insulated conductor in wire line 11 in a conventional rnnaner, spring 36 being maintained at all times in compression and in further compression when socket 12 is threaded to circulating head 14.

Lower shaft 27 is provided with a flange 37 welded thereto in the same manner that flange 32 is Welded to shaft 26 to abut an insulator plug 38- threaded into the bore 28 of circulating head 14. O-ring 39 is provided between plug 38 and circulating head 14, and an O-ring 4-6 is provided between plug 38 and shaft 27, both O-rings 39 and 40 being employed to provide a fluid-tight seal from the exterior to the interior of bore 28. Conventiorial electrical connectors at 41 and 42 are provided to connect insulated conductors at 43 and 44 to shaft 27.

Conductor 43 passes through an opening 45 in the wall of sleeve 36 downwardly through a wireway 46 therein to an electrical connector 47 fixed within tool connector 17. Conductor 44 is connected to explosive charge 29. A current is provided for explosive charge 29 via a lead 48 which extends through a hole 49 in the wall of sleeve 16 to a position under a bolt 50 threaded thereinto. Sleeve 16 is provided with large ports at 51, as shown in both FIGS. 1 and 2 to permit drilling mud to enter the interior of sleeve 16 as in the case of ports 24 in circulating head 14. A piston 52 is located inside of sleeve 16 to move from a position spaced from the upper end of connector 17 to a position closer thereto by the inrush of drilling mud through ports 24 and 51 following the detonation of explosive charge 29. Piston 52 is retained in the position shown in sleeve 16 by means of balls 53 which lie in depressions 54 in the internal surface of sleeve 16, balls 53 being maintained therein by a frangible disc 55. Disc 55 is provided with projections 56 to hold balls 53 in the position shown in FIGS. 2 and 3. Piston 52 is mounted and held in that position by locating balls 53 in depression 54 by inserting disc 55 with projections 56 on both sides of the balls and rotating disc 55 to the position shown in FIG. 3. A fiuid'tight seal is provided between piston 52 and the internal surface of sleeve 16 by means of an O-ring 57.

An insulated conductor 58 connects electrical connector 59 to gun perforator 19, whereby the application of a firing voltage to conductor 58 will fire gun perforator 19. Connectors 47 and 59 are respectively connected to electrical contacts 60 and 61 that are connected to each other by the operation of a pressure switch 62 located in connector 17. Pressure switch 62 is operative in response to a build-up of pressure inside sleeve 16 between piston 52 and the upper end of connector 17 to connect contacts 60 and 61 to tire gun :perforator 19.

In the operation of the embodiment of the invention illustrated in FIGS. 1, 2 and 3, before the tool is lowered int-o an oil well, piston 52 is located in the position shown in FIG. 2 spaced a substantial distance from the upper end of connector 17 with air filling the space therebetween. Tool 10, shown in FIG. 1, is then lowered into a well, O-ring 57 and an O-ring 63, between a shaft 64 of pressure switch 62 and the body of connector 17 maintaining the space between piston 52 and connector 17 fluid-tight. Tool 10 is lowered into drilling mud in a well to a position submerged in the drilling mud, and an electrical signal is applied to the internal conductor of wire line 11 to fire explosive charge 29.

When explosive charge 29 is detonated, frangible disc 55 is broken, balls 53 move out of depressions 54 in sleeve 16, and drilling mud rushes through ports 24 and 51 of circulating head 14 and sleeve 16 respectively and drives piston 52 downwardly within sleeve 16. Circulation fiuid thus fills the space above piston 52 as it becomes contiguous to the upper end of connector 17, thereby decreasing the pressure of the drilling mud at the position of or surrounding the tool it), including the perforator 19 in the well. Pressure inside sleeve 16 between piston 52 and the upper end of connector 17 is thus increased from atmospheric pressure to a substantially higher pressure, which increase in pressure operates pressure switch 62 to connect contacts 60 and 61, in which case perforator 19 is fired. Alternatively, shaft 64 of pressure switch 62 may protrude somewhat above the upper end of connector 17 to be actuated mechanically by movement of piston 52 downwardly in direct contact thereagainst and thereby in this case to connect contacts 60 and 61 to fire perforator 19. In this fashion perforator 19 is fired shortly before piston 52 reaches connector 17, whereby the perforator charges are expected before the circulation fluid impacts against connector 17 with a resulting increase in the circumjacent pressure.

In accordance with a special feature of the invention, a

spring 65 is provided to urge shaft 64 of pressure switch 62 upwardly, the force constant of spring 65 being selected in comparison to the space between the upper end of connector 17 and piston 52 to permit actuation of pressure switch 62 at a time subsequent to the detonation of explosive charge 29, but prior to a time that impact of the falling drilling mud column is created when it reaches its lower limit of travel. In this case, the penetration effected by perforator 19 into a formation is substantially improved not only by the reduced pressure at which it is permitted to operate after drilling mud is permitted to enter the space above piston 52 in its lowermost limit of travel, but also the impact of the falling drilling mud column will extend the fractures and cracks initiated by perforator 19.

An alternative embodiment of the invention is shown in FIG. 4. Only a portion of the tool of the invention is shown in FIG. 4, all the structure located above insul-ated conductors 43' and 44' being identical to the structure located above conductors 43 and 44 at a. position immediately above piston 52 in FIG. 2. Note will also be taken that with the exception of the different designation for the conductor 43 in FIG. 4 rather than the designation 43 therefor in FIG. 2, the entire structure shown below a position immediately above the upper end of connector 17 in FIG. 4 is identical to that shown in FIG. 2. A sleeve 16' is employed in FIG. 4 identical to sleeve 16 except for the portion to be specifically described in the immediately following paragraph.

A frangible disc 55 is shown in FIG. 4 seated on an O-ring 66 in the bore of sleeve 16 and is held in place therein by means of a snap ring 67. Frangible disc 55 is broken by detonation of an explosive charge 29 which may be located below frangible disc 55, or above it, as shown.

In the operation of the tool of the invention illustrated in FIG. 4, the tool may have an external appearance sub stantially the same as tool 10 shown in FIG. 1. The space between frangible disc 55 and the upper end of connector 17 is initially filled with air at atmospheric pressure. The tool then is submerged in drilling mud in an oil well at a point where perforation is desired. Explosive charge 29 is then detonated by the application of an appropriate voltage to conductor 44'. Detonation of explosive charge 29 then breaks frangible disc 55 and drilling mud rushes into the space below O-ring 66 within sleeve 16'. An increase in pressure in this space actuates pressure switch 62 located in the upper end of connector 17 at a time prior to the time maximum hydrostatic drilling mud pressure is reached due to the impact of the falling mud column in the well to fill the air space within sleeve 16' immediately above connector 17. Actuation of pressure switch 62 then fires perforator 19 and the adjacent formation is perforated at a reduced hydrostatic drilling mud pressure. Immediately thereafter, the impact of the falling mud column, due to its kinetic energy in falling in the well and filling the space immediately above connector 17, fractures the formation a further distance.

Another embodiment of the invention is illustrated in the FIG. 5, including a sleeve 16 which houses a piston and frangible disc assembly 52" identical to that shown in FIG. 4 including piston 52' and all the structure above it. A portion of gun perforator 19 is also shown in FIG. 5 threaded into a connector 17' that in turn is threaded into sleeve 16", a fluid-tight seal being provided there'- between by an O-ring 68. Connector 17 is simply a cylindrical hollow connector having a plug 69 threaded thereinto at its upper end. An insulated conductor 44 is connected to explosive charge 29" in the same manner that conductors 44 and 44' are connected to explosive charges 29 and 29 respectively. A conductor 43" is provided to perform substantially the same function as conductors 43 and 43'; however, insulated conductor 43 terminates in an electrical contact 70 located within the bore of sleeve 16". Another contact 71 is also located in the bore ,of sleeve 16", contact 71 being connected to an insulated conductor 72 which extends downwardly into gun perforator 19 and provides means for which the same may be fired when an appropriate potential is applied to the conductor 72.

The operation of the tool shown in FIG. 5 is as follows. Piston assembly 52 is located in the position shown in FIG. 5 with air at atmospheric pressure filling the space within sleeve 16 between the lower end of piston assembly 52" and the upper end of connector 17'. The tool, from the exterior, may look substantially the same as the tool shown in FIG. 1. In this condition, the tool is lowered into a well containing drilling mud to a depth therein such that the entire tool is submerged in the drilling mud. An appropriate voltage is supplied to conductor 44- to detonate explosive charge 29", whereupon the frangible disc of the assembly 52" is fractured and the piston thereof is driven downwardly within sleeve 16". In this case, the pressure in the well adjacent gun perforator 19 is reduced and at this point, prior to the time that the drilling mud column reaches its lower limit of travel, the piston of assembly 52" makes an electrical connection between contacts 70 and 71 to fire gun perforator 19. In this case, contacts 70 and 71 are appropriately located at a selected vertical position within the interior of sleeve 16" to fire gun perforator 19 at the appropriate time. The bullets of gun 19 thus then penetrate the adjacent formation under a reduced drilling mud hydrostatic pressure and the impact of the falling drilling mud column at its lower limit of travel after the bullets have entered the formation enlarges and extends the openings therein.

The following example is illustrative of the method of perforating a well in accordance with this invention. The well to be perforated is completed with casing cemented in place to a total depth of 10,000 feet. It is desired to perforate the casing at a promising oil producing limestone strata located at 9,970 to 9,985 feet. To accomplish this, a tool assembly as illustrated in FIG. 1 is made up with the perforator section being about 16 feet long and therefore of sufficient length to perforate into the feet of limestone.

The apparatus is lowered into the well bore through the drilling mud which is present therein to prevent uncontrolled flow of fluids following perforation. The mud has a density of 13 pounds per gallon. The apparatus is lowered on an electrically conductive wire line to the depth whereby the perforator is opposite and across the limestone at 9,970 to 9,985 feet.

The casing and formation are perforated by closing an electrical circuit at the earth surface. The circuit is connected via the conductive wire line 11 to the explosive charge 29. The charge explodes, destroying disc 55 and releasing piston 52 to traverse the hollow cylinder in sleeve 16. The drilling mud surrounding the perforator gun and pressing against piston 52 with a starting hydrostatic pressure of 6,700 p.s.i. drives the piston toward the switch 62. When the piston 52 has traversed about threefourths the length of the hollow cylinder, the switch 62 closes and fires the gun perforator 19.

The apparatus is withdrawn from the well and the well is put into fluid production. The rate of production shows the gun bullets penetrated through the casing and deeply into the formation, creating openings whereby the formation fluids readily enter the well bore.

From the foregoing, it will be appreciated that the reduced hydrostatic drilling mud pressure and the impact of the falling drilling mud Y column both substantially improve the perforation of the formation, or the casing and formation, surrounding :a well bore when the perforator is fired at a time between the time the pressure reduction is initiated and the time the dynamic hydrostatic pressure is at a maximum. Still further, the same reduced and the subsequently increased hydrostatic pressure may be used by itself for a cleaning or fracturing effect for purposes other than perforating, as well as for perforating, and in combination with other tools. When the hydrostatic pressure in a well is reduced, flow from a formation may be sustained to clean the same. Fracturing may he produced by the impact of the falling drilling mud column.

The word open as used in describing the initial function of each of the embodiments disclosed herein is defined hereby as describing the function of explosive charges 29 and 29 which fracture disc 55' and also is defined hereby as describing the function of explosive charge 29 in fracturing disc 55 to allow piston 52 to *be driven downwardly in sleeve 16 and thereby open the space below its position as shown in FIG. 2.

Although only three specific embodiments of the invention have been shown and described in detail herein, many other changes and modifications thereof will of course suggest themselves to those skilled in the art. The embodiments selected for this disclosure are merely illustrative and the present invention is not to be limited thereto, the true scope of the invention being defined only in the appended claims.

What is claimed is:

1. A combination tool comprising:

an elongated hollow body having an elongated hollow space therein;

fluid-tight closure means spaced 2. distance large in comparison to the maximum transverse dimension of said hollow space from the opposite end thereof;

means for opening said closure means;

passageway means through said body at said closure means to admit liquid to said hollow space when said closure means is opened, said passageway means having a total cross-section of a substantial size in comparison with that of said hollow space; and

means responsive to opening of said closure means for time delay controlled closing of an electrical c-ircui-t adapted to fire a perforator explosive charge when said hollow space is nearly filled by admitted liquid.

2. A combination tool as in claim 1, wherein the elongated hollow body is gas filled.

3. A combination tool comprising:

an elongated hollow body having an elongated hollow space therein;

closure means spaced a distance large in comparison to the maximum transverse dimension of said hollow space from the lower end thereof providing a fluid-tight seal therefor;

means for opening said closure means;

a pressure responsive device having a predetermined displacement volume for actuation thereof, said pressure responsive device being located in said hollow space a distance below said closure means such that the hollow space in said body between said responsive device and said closure means is several times greater in size than said predetermined dis placement volume; and

passagway means through said body at said closure means to admit circulation liquid to said space when said closure means is opened, said passageway means having a total cross-section of a substantial size in companion with that of said hollow space, said pressure responsive device being a pressure switch adapted to detonate a perforator explosive charge.

4. A combination tool comprising:

a hollow body having fluid-tight closure means;

a piston at one of the ends of said body adjacent said closure means;

means to open said closure means, whereby circulation liquid admitted to the interior of said body via said closure means will drive said piston toward the other end of said body;

a perforator having a firing circuit;

a pair of normally open contacts in the interior wall of said body spaced from said one end of said body and connected with said firing circuit; and

means on said piston responsive to movement thereof to a predetermined position spaced from said one end of said body for electrically connecting said contacts to close said firing circuit, said hollow body also defining a chamber above said closure means and having openings therein providing for circulation of well liquid from a bore hole and for transmission of an implosive shock wave set up when said piston is driven on its working stroke to fire said perforator.

References Cited by the Examiner UNITED STATES PATENTS Wells 175-45 X Piety 16643 X Babcock 175-456 Taylor 1754.54 Bourne 175-4.54 X

CHARLES E. OCONNELL, Primary Examiner.

D. H. BROWN, Assistant Examiner. 

1. A COMBINATION TOOL COMPRISING: AN ELONGATED HOLLOW BODY HAVING AN ELONGATED HOLLOW SPACE THEREIN; FLUID-TIGHT CLOSURE MEANS SPACED A DISTANCE LARGE IN COMPARISON TO THE MAXIMUM TRANSVERSE DIMENSION OF SAID HOLLOW SPACE FROM THE OPPOSITE END THEREOF; MEANS FOR OPENING SAID CLOSURE MEANS; PASSAGEWAY MEANS THROUGH SAID BODY AT SAID CLOSURE MEANS TO ADMIT LIQUID TO SAID HOLLOW SPACE WHEN SAID CLOSURE MEANS IS OPENED, SAID PASSAGEWAY MEANS HAVING A TOTAL CROSS-SECTION OF A SUBSTANTIAL SIZE IN COMPARISON WITH THAT OF SAID HOLLOW SPACE; AND MEANS RESPONSIVE TO OPENING OF SAID CLOSURE MEANS FOR TIME DELAY CONTROLLED CLOSING OF AN ELECTRICAL CIRCUIT ADAPTED TO FIRE A PERFORATOR EXPLOSIVE CHARGE WHEN SAID HOLLOW SPACE IS NEARLY FILLED BY ADMITTED LIQUID. 